1. Field of the Invention
The present invention relates to a dispersion containing an amphipatic lipid as a dispersoid, a washing-away type cosmetic composition which comprises the amphipatic lipid, has an emulsion-like or pearl-lustrous appearance and has low skin irritation, and another washing-away type cosmetic composition which comprises an amphipatic lipid having a definite average particle size, has an emulsion-like or pearl-lustrous appearance and has low skin irritation.
2. Description of the Related Art
With a view to imparting good appearance to a washing-away type cosmetic composition such as body shampoo, hair shampoo, rinse or the like which is washed away after application to the skin or hair, a dispersion of an emulsifying agent or a pearling agent is conventionally employed for such a composition to impart it an emulsion-like or pearl-lustrous appearance.
Such a washing-away type cosmetic composition contains a surfactant, which sometimes causes dry skin or inflammation. Surfactants not so irritating to the skin are therefore being developed, but development of a novel low-irritating surfactant needs tremendous time and cost.
There are several attempts made to incorporate an amphipatic lipid such as ceramide in a washing-away type cosmetic composition, thereby protecting the skin or hair. Described specifically, reported are a hair cosmetic composition comprising an amide derivative, which is a substance analogous to ceramide (Japanese Patent Application Laid-Open No. 9913/1989); a hair cosmetic composition comprising a glycoceramide and a cationic surfactant (Japanese Patent Application 502660/1994); and a cleansing or treatment composition for hair or skin which comprises an anionic surfactant, amphoteric surfactant, cationic polymer and ceramide or glycoceramide (Japanese Patent Application Laid-Open No. 59443/1996). In the above-described cosmetic compositions, however, only a small amount (about 2 wt. % at the maximum) of a ceramide can be incorporated stably because it is solid at room temperature. On the other hand, if the ceramide is incorporated in the cosmetic composition after it is dissolved in another medium and then emulsified, it does not exhibit sufficient effects.
An object of the present invention is therefore to provide a washing-away type cosmetic composition which can sufficiently exhibit properties of an amphipatic lipid which is in the solid form at room temperature and a dispersion employed for it.
In one aspect of the present invention, there are thus provided a dispersion comprising, in an aqueous medium, the following components (a) and (b):
(a) 5 to 40 wt. % of, as a dispersoid, an amphipatic lipid having, in the molecule thereof, at least one hydroxy and amide group; and
(b) 2 to 55 wt. % of a surfactant; and a washing-away type cosmetic composition comprising the dispersion.
In another aspect of the present invention, there is also provided a washing-away type cosmetic composition comprising the following components (A) and (B):
(A) 0.01 to 10 wt. % of an amphipatic lipid having an average particle size of 0.5 to 150 xcexcm and having, in the molecule of the amphipatic lipid, at least one hydroxy and amide group; and
(B) 5 to 95 wt. % of a surfactant.
The dispersion according to the present invention has, as a dispersoid, a solid-particulate amphipatic lipid dispersed in an aqueous medium. It is useful as a component for a washing-away type cosmetic composition having both good emulsion-like or pearl-lustrous appearance and having low skin irritation. The washing-away type cosmetic composition according to the present invention has, as described above, a good emulsion-like or pearl-lustrous appearance and in addition, has low skin irritation because the amount of the surfactant, which is contained in the composition, adsorbed to the skin is small.
The term xe2x80x9can amphipatic lipid which has, in the molecule of thereof, at least one hydroxy and amide groupxe2x80x9d means a natural ceramide or a synthetic ceramide, or a substance analogous thereto (pseudo-ceramide) available by the synthesis or the like of the natural or synthetic ceramide, which is in the solid form at room temperature (25xc2x0 C.). Examples of the amphipatic lipid include xe2x80x9cCeramide H03xe2x80x9d (trade name, product of Sederma S. A.), Ceramide II (trade name, product of Sederma S. A.), xe2x80x9cQuestamide Hxe2x80x9d (trade name, product of Quest International), xe2x80x9cCeramide TIC-001xe2x80x9d (trade name, product of Takasago International Corp.), and xe2x80x9cSofcare Ceramide SL-Exe2x80x9d (trade name; product of Kao Corp.). The amphipatic lipid is preferred to have a melting point not less than 30xc2x0 C., more preferably not less than 40xc2x0 C. in consideration of the stability of the dispersion or the like formed using it. Particularly preferred examples of the ceramide analogous substance available by synthesis include amide derivatives represented by the below-described formula (1) including the above-exemplified Sofcare Ceramide SL-E. 
wherein R1 and R2 are the same or different and each independently represents a linear or branched, saturated or unsaturated C7-39 hydrocarbon group which may be substituted by at least one hydroxyl group, and R3 and R4 are the same or different and each independently represents a hydrogen atom, a phosphate salt residue, a sulfate salt residue or a saccharide residue, with the proviso that at least one hydroxyl group is contained in the molecule.
In the formula (1), preferred as R1 are linear or branched, saturated or unsaturated C9-25 hydrocarbon groups, preferred as R2 are linear or branched, saturated or unsaturated, C10-26 hydrocarbon groups and preferred as R3 or R4 is a hydrogen atom.
The preparation process of the above-described amide derivative (1) is described specifically in Japanese Patent Application Laid-Open No. 228048/1987, Japanese Patent Application Laid-Open No. 216852/1988 and the like.
As the amphipatic lipid serving as the component (a), those exemplified above can be used either singly or in combination. In the dispersion of the present invention, it is incorporated in an amount of 5 to 40 wt. %, preferably 10 to 30 wt. %.
As the surfactant serving as the component (b) of the dispersion of the present invention, at least one surfactant selected from nonionic surfactants, anionic surfactants, amphoteric surfactants and the like ordinarily employed for cosmetics can be used. Among them, examples of the nonionic surfactant include alkyl polyglycosides, polyoxyalkylene alkyl or alkenyl ethers, polyoxyalkylene sorbitan fatty acid esters, sorbitan fatty acid esters, polyoxyalkylene sorbitol fatty acid esters, polyoxyalkylene glycerin fatty acid esters, polyglycerin fatty acid esters, fatty acid monoglycerides, polyethylene glycol fatty acid esters and fatty acid alkanol amides. Examples of the anionic surfactant include polyoxyalkylene alkyl ether acetic acids or salts thereof, N-acylamino acid salts, polyoxyalkylene alkyl ether sulfate salts, polyoxyalkylene alkyl ether phosphate salts, alkyl phosphate salts, N-acylmethyl taurine salts, alkyl sulfosuccinate salts, polyoxyalkylene alkylsulfosuccinate salts and fatty acid salts. Examples of amphoteric surfactant include alkylaminoacetate betaines, alkylamine oxides, alkylamidopropyl betaines, alkylhydroxysulfobetaines and amidoamino acids (imidazoline-type betaines).
Among them, preferred are nonionic surfactants and polyoxyethylene alkyl ether acetic acids or salts thereof. As the nonionic surfactant, that selected from alkyl polyglycosides, polyoxyalkylene alkyl or alkenyl ethers, polyoxyalkylene sorbitan fatty acid esters and sorbitan fatty acid esters is preferred.
Particularly preferred examples of the nonionic surfactant include alkyl polyglycosides, for example, those in which the alkyl group has 8 to 14 carbon atoms and the condensation degree of glucose is 1 to 2; polyoxyalkylene alkyl or alkenyl ethers, for example, those in which the alkyl or alkenyl group has 8 to 18 carbon atoms and the number of moles of the added ethylene oxide is 4 to 25, preferably 4 to 15 on average; polyoxyalkylene sorbitan fatty acid esters in which the fatty acid has 8 to 20 carbon atoms and the number of moles of the added ethylene oxide is 5 to 25 on average; and sorbitan fatty acid esters, for example, monoesters of a C8-20 fatty acid. Examples of the polyoxyethylene alkyl ether acetic acid and salt thereof include polyoxyethylene alkyl ether-acetic acids which have 8 to 20 carbon atoms and in which the number of moles of the added ethylene oxide is 3 to 15 on average and alkali metal salts thereof. In other words, polyoxyethylene alkyl ether acetic acids can be used as they are without neutralization or after neutralized as needed. The further addition of a cationic surfactant can heighten adsorption of an amphipatic lipid to the skin or hair.
As the component (b), the above-exemplified surfactants may be used either singly or in combination. It is added in an amount of 2 to 55 wt. %, preferably 5 to 40 wt. % to the dispersion of the present invention.
Here, the amphipatic lipid (a) and surfactant (b) are added at an (a)/(b) weight ratio of 90/10 to 25/75, preferably 80/20 to 30/70, particularly preferably 70/30 to 40/60.
The dispersion according to the present invention can be prepared, for example, by heating a mixture of the amphipatic lipid (a), the surfactant (b) and water to the melting point of the amphipatic lipid or higher (melting point to melting point+about 10xc2x0 C.), thereby fusing it while stirring; and after the resulting mixture becomes uniform, cooling it while stirring to crystallize the component (a).
The particle size of the component (a) can be controlled by adjusting the kind or amount of the surfactant, cooling rate, stirring speed or the like. The component (a) is preferred to have an average particle size, as measured by the method described later, of 0.5 to 150 xcexcm, more preferably 1 to 150 xcexcm, particularly preferably 1 to 80 xcexcm. To the dispersion of the present invention, it is possible to add ethylene glycol distearate, ethylene glycol monostearate, another pearling agent, emulsifying agent, pH regulator, antiseptic or the like before or after the above-described heating, fusing or cooling.
The dispersion of the present invention thus obtained has an emulsion-like or pearl-lustrous appearance so that incorporation of it in a washing-away cosmetic composition makes it possible to impart the cosmetic composition with an emulsion-like or pearl-lustrous appearance, and in addition, to reduce the amount of the surfactant, which is contained in the washing-away cosmetic composition, adsorbed to the skin, thereby reducing the skin irritation caused by the surfactant.
Examples of the washing-away type cosmetic composition of the present invention include hair cosmetic compositions such as shampoo and rinse, facial ones such as face wash and facial pack and those for systemic application such as massage oil, cream and the like and body shampoo. The dispersion according to the present invention is particularly useful as a component of a cleansing agent containing a surfactant as a base, such as systemic cleansing agent, hand and finger cleansing agent and facial wash.
The amount of the invention dispersion to be added to a washing-away type cosmetic composition may be adjusted as needed, depending on the kind of the cosmetic composition or concentration of the dispersion. Amphipatic lipid concentrations ranging from 0.01 to 10 wt. %, particularly, 0.1 to 5 wt. % are usually preferred.
Upon preparation of a washing-away type cosmetic composition by using the dispersion of the present invention, it is preferred to premix components of the cosmetic composition other than the dispersion and then mix the resulting mixture with the dispersion at not more than 50xc2x0 C. Such a procedure makes it possible to stably incorporate the amphipatic lipid, which has been contained in the dispersion, in the cosmetic composition.
As the surfactant to be used for the washing-away type cosmetic composition prepared using the dispersion, those exemplified later as the component (B) can be mentioned as examples. The amount of the surfactant is, based on the amount of the washing-away type cosmetic composition, 5 to 95 wt. %, preferably 10 to 50 wt. %, more preferably 10 to 35 wt. % in terms of the total amount of the surfactants used for the preparation of the dispersion and the washing-away type cosmetic composition.
As the amphipatic lipid (A) to be used for the washing-away type cosmetic composition of the present invention, amide derivatives (1) are particularly preferred similar to the case of the component (a) in the above-described dispersion. They may be used either singly or in combination, but an average particle size of it (them) is preferably 0.5 to 150 xcexcm, more preferably 1 to 150 xcexcm, still more preferably 1 to 80 xcexcm, particularly preferably 1 to 50 xcexcm from the viewpoints of the irritation reducing effects and stability in the washing-away type cosmetic composition. The term xe2x80x9caverage particle sizexe2x80x9d as used herein means an arithmetically calculated average length, in a straight line, of the longest portions of 30 particles selected optionally from a micrograph of the washing-away type cosmetic composition taken by an optical microscope under a transmitted light. The amphipatic lipid (A) is added in an amount of 0.01 to 10 wt. %, preferably 0.1 to 5 wt. % to the washing-away type cosmetic composition of the present invention.
As the surfactant (B), those exemplified above as the component (b) of the dispersion and those ordinarily added to a washing-away type cosmetic composition for the purpose of cleansing or softening of the hair can be mentioned. Preferred examples include alkyl polyglycosides, fatty acid alkanol amides, amidoamino acid surfactants (imidazoline betaines), alkylaminoacetate betaines, alkylamine oxides, alkylamidopropyl betaines, alkylhydroxysulfobetaines and anionic surfactants, with alkyl polyglycosides, amidoamino acid surfactants (imidazoline betaines) and anionic surfactants being more preferred. Among the anionic surfactants, preferred are polyoxyalkylene alkyl ether sulfates, for example, those containing an alkyl group having 12 to 18 carbon atoms and having 2 to 4 moles on average of added ethylene oxide; fatty acid salts, for example, those containing a fatty acid having 12 to 18 carbon atoms; alkyl phosphates, for example, those containing an alkyl group having 12 to 18 carbon atoms; polyoxyalkylene alkyl ether phosphates, for example, those containing an alkyl group having 12 to 18 carbon atoms and having 1 to 5 moles on average of added ethylene oxide; polyoxyalkylene alkyl ether acetates, for example, those containing an alkyl group having 12 to 18 carbon atoms and having 3 to 12 moles on average of added ethylene oxide; acylated amino acid salts, for example, those containing an acyl group having 12 to 18 carbon atoms and being a derivative of alanine, sarcosine, glycine or glutamic acid; alkyl sulfate salts, alkyl sulfosuccinate salts and polyoxyethylene alkylsulfosuccinate salts each containing an alkyl group having 12 to 18 carbon atoms; and acylated isethionate salts and N-acylmethyltaurine salts each containing an acyl group having 12 to 18 carbon atoms. Preferred examples of the salt include salts soluble in water such as alkali metal salts and alkanolamine salts. The surfactant serving as the component (B) is added in an amount of 5 to 95 wt. %, preferably 10 to 50 wt. %, more preferably 10 to 35 wt. % based on the washing-away cosmetic composition of the present invention.
To the washing-away cosmetic composition of the present invention, it is possible to add optionally an oil such as higher alcohol, lanolin, squalane, hydrocarbon or silicone; a cationized polymer such as cationized cellulose, cationized guar gum or xe2x80x9cMercoat 550xe2x80x9d (product of Merck and Co., Inc); a water-soluble macromolecule such as methyl cellulose, hydroxyethyl cellulose, carboxyvinyl polymer or polysaccharide (xanthan gum, etc.); a viscosity regulator or solubilizing assistant such as polyoxyalkylene sorbitan ester, polyoxyethylene fatty acid ester, ethanol, glycerin or sorbitol; a chelating agent such as ethylenediamine tetraacetate (EDTA) or phosphate salt; an antiseptic such as methyl paraben or butyl paraben; a nutrient such as vitamin or precursor thereof; an animal or vegetable extract such as lecithin or gelatin, or derivative thereof; a fine-particulate polymer such as nylon or polyethylene; an anti-inflammatory agent such as dipotassium glycyrrhizinate or allantoin; a bactericide or anti-dandruff agent such as benzalkonium chloride, benzalkonium cetylphosphate (xe2x80x9cSANISOL Pxe2x80x9d, trade name; product of Kao Corporation), triclosan, trichlorocarban, octopirox or zinc pyrithione; an antioxidant such as dibutylhydroxytoluene; an ultraviolet absorber; a pH regulator; a colorant; a perfume; and/or the like.
Upon preparation of the washing-away cosmetic composition of the present invention, an amphipatic lipid may be used as is or in the form of a dispersion, and preferably used in the form of a dispersion. When the amphipatic lipid is used as is, it is preferred to dissolve the amphipatic lipid together with the other components of the cosmetic composition by heating or to disperse them uniformly, and then cool the whole mixed system to crystallize the amphipatic lipid.
The washing-away type cosmetic composition of the present invention can be converted into any dosage form such as solid, paste or liquid.